- Mar 5, 2020
- 3,114
- Pool Size
- 66000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Astral Viron V35
Unexplained pH rise
- Thread starter xDom
- Start date
- Nov 12, 2017
- 11,950
- Pool Size
- 12300
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
TFP likes CSI, which, if I remember correctly, is a derivative of LSI. LSI was originally developed for some other industrial purpose, CSI was the modification for use with pools. I probably mangled some of that, but it's close.
There is a CSI calculator in the Pool Math app. Or you can use the original version. It's a webpage, and the link is at the bottom of every TFP website page, named "Old PoolMath Webpage."
The webpage requires you fill in all your pool's levels. The calculator in the Pool Math app uses your current or latest test result entries, which makes it very convenient.
I used the webpage for my calculation above, but I use the Pool Math calculator each time I run a suite of tests. I monitor CSI weekly. As the annual conditions change, especially pool water temperature, I use the calculator to adjust my pH. As the water cools, I have to allow my pH to rise, in order to keep my CSI between -0.3 and 0. During the summer, I drop my pH to keep my CSI as close to -0.3 as possible. -0.3 is best for SWGs, as that slightly lower number keeps the SWG's internal plates free of calcium deposits. If you don't have an SWG, then 0 is the target, but anything between -0.3 to 0.3 is fine.
While TA, CH, CYA and Salt levels are all used in the CSI calculation, it is water temp and pH that affect CSI the most. Since I have no control over water temp, I use pH to counter the effects the water temp has on my CSI. They are inversely proportional. The higher the water temp, the lower the pH, and vice versa. FC doesn't affect CSI.
It's very much simpler than it sounds, especially using the Pool Math app. You'll find that if you're maintaining all your levels within TFP ranges, the CSI will also be within TFP's CSI range. EZPZ.
There is a CSI calculator in the Pool Math app. Or you can use the original version. It's a webpage, and the link is at the bottom of every TFP website page, named "Old PoolMath Webpage."
The webpage requires you fill in all your pool's levels. The calculator in the Pool Math app uses your current or latest test result entries, which makes it very convenient.
I used the webpage for my calculation above, but I use the Pool Math calculator each time I run a suite of tests. I monitor CSI weekly. As the annual conditions change, especially pool water temperature, I use the calculator to adjust my pH. As the water cools, I have to allow my pH to rise, in order to keep my CSI between -0.3 and 0. During the summer, I drop my pH to keep my CSI as close to -0.3 as possible. -0.3 is best for SWGs, as that slightly lower number keeps the SWG's internal plates free of calcium deposits. If you don't have an SWG, then 0 is the target, but anything between -0.3 to 0.3 is fine.
While TA, CH, CYA and Salt levels are all used in the CSI calculation, it is water temp and pH that affect CSI the most. Since I have no control over water temp, I use pH to counter the effects the water temp has on my CSI. They are inversely proportional. The higher the water temp, the lower the pH, and vice versa. FC doesn't affect CSI.
It's very much simpler than it sounds, especially using the Pool Math app. You'll find that if you're maintaining all your levels within TFP ranges, the CSI will also be within TFP's CSI range. EZPZ.
If you don't already see it on the main parameter page, go to settings in poolmath and 'track csi' and it'll then show up. (The same for salt, temp, borates, etc)
- Mar 5, 2020
- 3,114
- Pool Size
- 66000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Astral Viron V35
LSI and CSI are essentially the same thing. The LSI is a CSI that was named after Mr. Langlier. CSI stands for "Calcite Saturation Index". Calcite is a form of Calcium Carbonate, aka scale.
It's essentially just a measure for how saturated the water is with calcium and carbonate. The trick is to bring all the relevant input parameters in the formula into relation with parameters that are accessible with pool test kits and the right units. TA is for example used as a measure for the carbonate concentration. But you first have to deduct the CYA-contribution to TA and, if present, that of Borates.
The "traditional" LSI makes some simplifications and assumptions that are not great for our purposes.
The CSI that we are using (as calculated with PoolMath) goes back to an approach that Chem Geek used and documented in his spreadsheet, going back to first principals, and makeing the required simplifications and approximations in a way that is suitable to how pool water is typically composed.
There is for example an effect called "ionic strength" where you consider the effect that ions in the vicinity of a specific ion that you are trying to "count" are shielding that specific ion, and effectively make the concentration of that specific ion type appear a bit lower than a literal particle count would yield. Chemists talk in this situation about "activities" rather than concentrations that are relevant for chemical calculations.
Anyway, the point I want to make is that to calculate that shielding effect of your specific ion type you need to make assumptions about what is in your water that has shielding capabilities, how that stuff got into the water, and what usually comes with this stuff, but may not typically be tested for, so you don't actually know that this extra stuff is in the water but it's reasonable to assume that it is there in a typical use case. And that's where it is important to make assumptions based on typical pool water composition, rather than for example water in a heating system that Langlier was originally interested in.
Many other tools or apps use essentially the same formula for their saturation index calculation. Some might also call it CSI like we do, others might call it LSI, but it's actually the same thing. Others might use a different formula, that is based on the same first principles but different assumptions and approximations along the way, and call it CSI. Or LSI. Can be confusing.
That's why we like to use the same tool when talking about the saturation index. Which is PoolMath.
We call it CSI. Some pool tech using PoolMath may call it LSI because he's always called it that way, and so do all his mates. I don't really care how someone calls it - as long as it's been calculated with PoolMath. Because then I can put it into context, and can compare pool A with pool B.
It's essentially just a measure for how saturated the water is with calcium and carbonate. The trick is to bring all the relevant input parameters in the formula into relation with parameters that are accessible with pool test kits and the right units. TA is for example used as a measure for the carbonate concentration. But you first have to deduct the CYA-contribution to TA and, if present, that of Borates.
The "traditional" LSI makes some simplifications and assumptions that are not great for our purposes.
The CSI that we are using (as calculated with PoolMath) goes back to an approach that Chem Geek used and documented in his spreadsheet, going back to first principals, and makeing the required simplifications and approximations in a way that is suitable to how pool water is typically composed.
There is for example an effect called "ionic strength" where you consider the effect that ions in the vicinity of a specific ion that you are trying to "count" are shielding that specific ion, and effectively make the concentration of that specific ion type appear a bit lower than a literal particle count would yield. Chemists talk in this situation about "activities" rather than concentrations that are relevant for chemical calculations.
Anyway, the point I want to make is that to calculate that shielding effect of your specific ion type you need to make assumptions about what is in your water that has shielding capabilities, how that stuff got into the water, and what usually comes with this stuff, but may not typically be tested for, so you don't actually know that this extra stuff is in the water but it's reasonable to assume that it is there in a typical use case. And that's where it is important to make assumptions based on typical pool water composition, rather than for example water in a heating system that Langlier was originally interested in.
Many other tools or apps use essentially the same formula for their saturation index calculation. Some might also call it CSI like we do, others might call it LSI, but it's actually the same thing. Others might use a different formula, that is based on the same first principles but different assumptions and approximations along the way, and call it CSI. Or LSI. Can be confusing.
That's why we like to use the same tool when talking about the saturation index. Which is PoolMath.
We call it CSI. Some pool tech using PoolMath may call it LSI because he's always called it that way, and so do all his mates. I don't really care how someone calls it - as long as it's been calculated with PoolMath. Because then I can put it into context, and can compare pool A with pool B.
- May 3, 2014
- 58,787
- Pool Size
- 6000
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
You have a fiberglass pool. CSI is not a concern unless your CH is greater than 500 or so.
CSI is calculated by PoolMath.
CSI is calculated by PoolMath.
- Nov 12, 2017
- 11,950
- Pool Size
- 12300
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
Ahg! xDom's pool is fiberglass!? Where did I cross that wire!?!
@xDom, please fill in your signature. We base our advice on it (or get confused about it!!). A signature something like mine is especially helpful. You were asking about LSI and CSI and I mis-assumed.
https://www.troublefreepool.com/account/signature
- Jan 4, 2016
- 5,293
- Pool Size
- 44000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
Sounds like terminating the 1kg (2.2 lbs) of alkalinity increaser per six weeks is the first step.
I would double-check the alkalinity testing, carefully reviewing the method with the CCL kit, and/or for $30 or $35, you could cross check it with an Aussie Gold 4in1 test kit and same caveat on following the test instructions to the letter. Aussie Gold kits are heaps reliable for TA (and pH).
Your TA would have risen over time, just as your CH has risen from 80 to 300 ppm over time, but for the acid. CH accumulates in the pool. TA is killed by acid additions. You likely only need to test CH once or twice a year in your fibreglass pool, watching out for higher accumulation, which you may never see. Saturation indexes can be ignored.
The Acid-TA roller coaster is a pool chemical industry racket - raising TA with 'alkalinity up', 'buffer' etc.... so acid needed to bring it down... then buffer again... then acid again... rinse and repeat. Bread and butter for a pool store, with an independent target of 100+ (some say 120+). 50-90 ppm TA is fine. TFPC will help you confidently get off that crazy train.
p.s. I haven't added any alkalinity increaser for around 6 years in concrete pools where saturation indexes matter, aside from using a bit while brand new plaster was curing.
I would double-check the alkalinity testing, carefully reviewing the method with the CCL kit, and/or for $30 or $35, you could cross check it with an Aussie Gold 4in1 test kit and same caveat on following the test instructions to the letter. Aussie Gold kits are heaps reliable for TA (and pH).
Your TA would have risen over time, just as your CH has risen from 80 to 300 ppm over time, but for the acid. CH accumulates in the pool. TA is killed by acid additions. You likely only need to test CH once or twice a year in your fibreglass pool, watching out for higher accumulation, which you may never see. Saturation indexes can be ignored.
The Acid-TA roller coaster is a pool chemical industry racket - raising TA with 'alkalinity up', 'buffer' etc.... so acid needed to bring it down... then buffer again... then acid again... rinse and repeat. Bread and butter for a pool store, with an independent target of 100+ (some say 120+). 50-90 ppm TA is fine. TFPC will help you confidently get off that crazy train.
p.s. I haven't added any alkalinity increaser for around 6 years in concrete pools where saturation indexes matter, aside from using a bit while brand new plaster was curing.
Last edited:
- Mar 5, 2020
- 3,114
- Pool Size
- 66000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Astral Viron V35
Not quite there yet, doing TFPC for 3 or 4 years now, haven't added any TA up since. Bought a big 20 kg bag just before that. Let's buy big they said, it'll be cheaper they said. Wife is slowly munching through it now in the garden.
That was me adding Calcium. There are so many conflicting views and opinions on pool care. I read somewhere that keeping the CSI from being too far negative is prudent in a FG pool.
I at least like to keep the CSI above the -0.6. In winter with the low water temp and the low TA, CH is a way to help.
Yes it seems I’m stuck in the TA/pH loop.
I didn’t think about the TA rising over time, I thought it would decrease!
I guess it did with me pouring so much MA in.
My plan is to cut back on the TA increaser and to not add acid until it’s 1 point higher.
I’ll add at 8.1 instead of 8..
How does this sound?
Edit: well there’s been an improvement from when I first got the pool in August ‘22.
The installer told me to keep the pH at 7.2. Pool shop said 7.4, I was dumping in 5 litres every three weeks. Just thought that was normal
Last edited:
- Jan 4, 2016
- 5,293
- Pool Size
- 44000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
That sounds fine to me. I add acid when I see pH of 8.0 and correct to 7.8 and that works out to about once every two weeks in summer. I tend not to need any acid in winter.
As sources of info, my experience has been that pool builders and pool stores, on average, are equally misleading and uninformed about pool water chemistry.
As sources of info, my experience has been that pool builders and pool stores, on average, are equally misleading and uninformed about pool water chemistry.
- Nov 12, 2017
- 11,950
- Pool Size
- 12300
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
That's what I have found, except add weekly pool maintenance companies to the list. I read story after story here about builders who know nothing about water chemistry. Which, while lame, is somewhat excusable as that is not their business nor expertise.
No such excuse for a pool maintenance company, which I experienced personally. The entire staff, from the owner to the manager to each and every one of the ever-revolving maintenance guys, didn't have a clue about pool water chemistry. They'd show up once a week, test, dump the test chemicals into my pool, then blast it with gallons of chlorine and acid all at once, and brush for five minutes (tops). They'd fill the tab feeder, of course, but never tested CYA. I wouldn't be able to get in for a couple days, and by the end of the week my walls were tinged with green. With the CYA off the charts, I doubt my pool was ever sanitary.
Their solution for the pH blasting was to sell me an SWG, which they didn't have the slightest idea how to adjust. For the green, get this, they turned up the pump runtime and RPM!
Firing them was especially satisfying.
I bet if you questioned them their response would be
“ I’ve been doing this for 20 years! “
Water chemistry doesn’t care how long you’ve been testing pools for.
- Nov 12, 2017
- 11,950
- Pool Size
- 12300
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
That is the war-cry of the underachiever. I hear that a lot (sometimes "25 years" or "30 years"), and all that says to me is: "I'm still doing it how I did it 20 years ago, and I haven't learned a thing about it since."
Last edited:
- Nov 12, 2017
- 11,950
- Pool Size
- 12300
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
Exactly. They learned their "craft" from their boss before them. Who would make the same claim "You do it my way. I know what I'm doing. I've been doing this for 20 years."Who's to even say they had a clue when they started ?
That's really all that they learned, that's all that stuck. How to say "I've been doing this for 20 years!"
- Jan 4, 2016
- 5,293
- Pool Size
- 44000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
I woke up this morning realising I said this wrong for your situation.
IIRC, mgtfp mentioned earlier that keeping CSI between 0.0 and -0.3 will help keep your saltwater chlorinator free of scale between the plates inside the salt cell, which is good advice.
CSI can be found in the PoolMath app or on the old PoolMath webpage where it's calculated for you.
App: PoolMath
Webpage: PoolMath
- Mar 5, 2020
- 3,114
- Pool Size
- 66000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Astral Viron V35
I think this time it was Proavia who mentioned that. But yes, good advice.
- Sep 23, 2015
- 1,598
- Pool Size
- 20000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Astral Viron V25
Unfortunatly they’ve often been doing it wrong for 20 years or longer. Politely pointing that out to them will get you banded from FB pages.
That’s a badge of honour I’m proud to wear but feel sorry for everyone that blindly excepts their dribble.I haven’t added any bicarb for over 10 years. It’s quite useful on the dog‘s toilet area.
All the fibreglass companies here recommend a pH of 7.2-7.4 but don’t say why and its a non negotiable warrantee condition - disgraceful. The pH range in our AU standard for domestic pool water quality is given as 7.0 - 7.8 which means all these FG pools are not built to the AU standard.
- Jan 4, 2016
- 5,293
- Pool Size
- 44000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
I'm starting my testing of testing supplies and I noticed some progress. My old original 4in1 Aussie Gold comparator block shows 7.2-7.4 as "ideal for fibreglass pools" and "7.4 to 7.6 as ideal for concrete pools" The new one just shows one band called "Ideal" at 7.4 to 7.6
- Jan 4, 2016
- 5,293
- Pool Size
- 44000
- Surface
- Plaster
- Chlorine
- Salt Water Generator